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Necanicum Estuary Inches Closer To Wastewater Treatment Plant

Seaside Public Works Director Neal Wallace counts “five, 10, 15,” as he paces off the distance between the fence-line of the Wastewater Treatment Plant and the steep drop-off into the Necanicum Estuary, immediately to the north.

The ever-changing estuary, where the Necanicum River and Neawanna and Neacoxie Creeks join as they flow into the Pacific Ocean, is moving ever closer to the plant that treats all of Seaside’s sewage.

Wallace said he is getting worried – so much so that he moved a new building being constructed on the site.

“We wanted to save that space for future development,” Wallace said. “We were going to set (the new building) just outside the fence. We would have had to move the fence 20 or 30 feet. The more I thought about that, the more I started waking up at night – we changed the building location.”

The new building will house a belt press and dryer. Both pieces of equipment allow the wastewater treatment plant to convert sludge to biosolids and then process the biosolids enough to sell it to be used for compost.

Wallace said the $1.3 million project will allow the city to reduce the cost of processing sludge to between 8 and 9 cents per gallon. The cost in recent years had been as high as 26 cents per gallon.

Wallace said the first line of defense for the facility is a rock revetment installed by the U.S. Army Corps of Engineers after extreme erosion in 1949.

The revetment runs parallel to most of the current fence line at the rear of the property and is buried under several feet of sand.

“The thing that bothers me is that it is down low enough that stuff will just come over the top,” Wallace said. “The footing may be OK, but I think waves will just come right over the top.”

History has played a big role in the range of the estuary erosion.

During the 1960s, a developer began mining sand on the beach and dumped much of it north of the current wastewater plant. The developer planned to build luxury homes on the reclaimed land.

While no homes were ever built, the land stayed intact for many years.

Storms, including a big one in 1997, eventually breached the spit, said Tom Horning, local engineering geologist. Since then, the estuary has returned to a more normal flow.

One major issue contributing to the erosion near the plant, Horning said, is an immovable pile of rocks, remnants of the development in the 1960s, covered by sand and vegetation in the middle of the estuary. He said the water tends to flow further south as a result.

“If the city wanted to minimize the focusing of the channel to the south, they would want to take out that rock pile,” Horning said. “If we got the rock out of there, I think the river would act more within its natural range.”

Both Horning and Wallace say the weather should start working in their favor.

In the winter, winds are typically out of the south, southwest and help contribute to the erosion near the plant.

“Once we get into the nicer weather,” Wallace said, “the prevailing wind comes out of the northwest, currents change, the tides are different and yes, (this end of the estuary) tends to fill in.”

Horning said it appears to him that that may have already started.

After similar erosion caused concern in 2004 or 2005, Wallace contacted state and federal officials about doing work to protect the facility.

The army corps studied the potential fixes for the site. Ultimately the corps decided the best course of action was to do nothing.

Wallace said the corps felt the revetment that had already been installed was still doing the job it was intended to do.

“What we were told at that point is that the corps’ job is to protect public infrastructure,” Wallace said. “If this plant starts to sustain damage, we were told they would be here. I guess that’s the contingency plan.”

Horning sounded cautiously optimistic about the erosion near the plant.

“My guess is, the treatment plant is going to get away by the skin of its teeth this time around,” Horning said.